ENGINE BREAK IN

Hi, I recently rebuilt my 1.0 3 cylinder geo metro motor and used nippon piston rings when rebuilding. What I have noticed is that when driving above 55mph the car smokes excessively and loses oil fast. But if speed is maintained under 55mph it does not smoke and loses very little to no oil. The car was driven 600 miles around town before attempting to drive on the highway. I am wondering if anyone knows what the proper time should be to seat the rings or if this is not the rings and something else that is causing this. The smoke is oil since there is oil in the exhaust, the car is not running rich, and not losing water.